How to Unshrink a Sweater That Came Out Too Small

Your favorite sweater went into the dryer by mistake, and now the sleeves stop above your wrists and the body barely covers your waistband. Before you give it to a smaller relative, know this: you can often unshrink a sweater at home with a basin, some hair conditioner, and about an hour of patience.

It will not work on every fabric, and it will not restore every last centimeter. But on wool, cashmere, and most cotton knits, I regularly get back 70 to 90 percent of the lost size. Here is exactly how I do it with clients' sweaters and my own.

Why sweaters shrink in the first place

Knit fibers are stretched and set during manufacturing. Heat, water, and tumbling let them relax back into a tighter shape. Wool has an extra problem: its fibers are covered in tiny scales that lock together when agitated in warm water. That process is called felting, and it is why a wool sweater can shrink by a full size in a single hot cycle.

Cotton shrinks differently. The fibers swell in water and contract as they dry, especially under heat. Cotton shrinkage is usually easier to reverse because the fibers have not physically matted together.

This matters because the fix is the same in both cases (relax the fibers, then reshape while damp), but your expectations should differ. A lightly shrunk cotton crewneck can come back almost fully. A felted wool sweater that now feels thick and stiff, like a boiled blanket, probably will not.

What you need to unshrink a sweater

• A clean sink, basin, or bathtub
• Lukewarm water, around 30 C (86 F), roughly the temperature of a baby's bath
• Hair conditioner or baby shampoo, about 2 tablespoons per 4 liters of water
• Two large bath towels
• A flat drying rack or a spare towel on a table
• A tape measure and, ideally, a sweater that fits you correctly to use as a template

Conditioner works because it coats the fibers and lets them slide past each other. Fabric softener is an option too, but I find conditioner leaves less residue on wool.

Step by step: the soak and stretch method

1. Measure the original fit. Lay a sweater that fits you on a flat surface and note the chest width (armpit to armpit), body length, and sleeve length. Write the numbers down.
2. Mix the soak. Fill the basin with lukewarm water and stir in the conditioner until it disperses.
3. Soak for 30 minutes. Submerge the sweater and press gently so it fills with water. Do not rub or wring it. Set a timer and leave it alone.
4. Press out the water. Lift the sweater out in a bundle, supporting its weight so it does not stretch unevenly. Press it against the side of the basin. Do not rinse out the conditioner.
5. Roll it in a towel. Lay the sweater flat on a dry towel, roll the towel up like a sleeping bag, and press along the roll. The sweater should be damp, not dripping.
6. Stretch to size. Lay it on the second towel and gently pull in short movements, working from the center outward. Use your template sweater or measurements as a guide. Pull the body lengthwise first, then the chest, then each sleeve.
7. Pin or weight it. If it keeps springing back, place a few heavy books along the hem and cuffs, or use rust proof pins into a foam board.
8. Dry flat. Leave it for 24 to 48 hours away from radiators and direct sun. Turn it over once halfway through.

If it comes out still a little short, repeat the whole process. A second round often recovers another 2 to 3 centimeters.

Expected results by fabric

Why I do not recommend the vinegar and borax tricks

You will find advice online to soak shrunk sweaters in white vinegar, borax, or Epsom salt. I have tried all three side by side with conditioner, on matching cotton sweaters I shrank on purpose. Conditioner won every time.

Vinegar can help loosen cotton slightly, but it does little for wool and leaves a smell that needs a second rinse, which partly undoes the relaxing effect. Borax is alkaline, and alkaline solutions can weaken protein fibers like wool and cashmere over repeated use. Epsom salt showed no measurable difference from plain water in my tests.

The bigger issue is the idea that a soak does the real work. It does not. The stretching and flat drying are what restore the shape. A cheap bottle of conditioner simply makes the fibers easier to move. Spend your effort on step six, not on hunting for the perfect additive.

How to stop it happening again

Prevention is mostly about keeping knits out of the dryer and away from hot water. Our guide on how to wash clothes so they actually last covers water temperatures and spin speeds in more depth, but these are the habits that matter most for sweaters.

• Wash wool and cashmere by hand or on a wool cycle at 30 C or below. If you are unsure of the technique, follow our walkthrough to hand wash a wool sweater.
• Keep a separate laundry bag for anything that must air dry, so it never ends up in the dryer by mistake.
• Always dry knits flat. Hanging a wet sweater stretches the shoulders and can make it longer but narrower.
• Store sweaters folded, not hung. Our tips on storing clothes off season apply to everyday drawers as well.

When to stop trying and repurpose it

If you have done two full rounds and the sweater is still more than a size too small, accept it. A felted wool sweater makes good mittens, a hot water bottle cover, or a cushion front, because felt does not unravel when cut. A shrunk cotton sweater can become a cropped layer over a dress or a high waisted skirt, which is a look worth trying before you write it off.

Frequently asked questions

Can you unshrink a sweater that went in the dryer?

Yes, in most cases, as long as it is cotton, wool, or cashmere and has not felted. Soak it in lukewarm water with conditioner for 30 minutes, then stretch it to size and dry it flat. Synthetic sweaters damaged by heat rarely recover.

How long does it take to unshrink a sweater?

The hands on part takes about 45 minutes, including the soak. Drying flat takes another 24 to 48 hours depending on the thickness of the knit and how warm your room is. Plan on two days before you can wear it.

Does hair conditioner damage wool?

Not in the small amount used for a single soak. Conditioner is designed for hair, which is also a protein fiber like wool. Leaving it in is fine, though you can give the sweater a quick, gentle rinse on its next wash.